Memory system

Abstract

A memory system includes a volatile first storing unit, a nonvolatile second storing unit in which data is managed in a predetermined unit, and a controller that writes data requested by a host apparatus in the second storing unit via the first storing unit and reads out data requested by the host apparatus from the second storing unit to the first storing unit and transfers the data to the host apparatus. The controller includes a management table for managing the number of failure areas in a predetermined unit that occur in the second storing unit and switches, according to the number of failure areas, an operation mode in writing data in the second storing unit from the host apparatus.

What is claimed is: 
     
         1 . A memory system comprising:
 a nonvolatile memory including a plurality of blocks; and   a controller configured to:
 generate a free block by controlling the nonvolatile memory; 
 manage a number of free blocks in the nonvolatile memory; 
 manage a number of bad blocks in the nonvolatile memory; and 
 determine whether or not the memory system is approaching an end of lifespan on the basis of the number of free blocks or the number of bad blocks; wherein, 
   after it is determined that the memory system is approaching the end of lifespan based on the number of free blocks or the number of bad blocks, a data write operation to the blocks in the nonvolatile memory becomes prohibited and a data write operation mode to the blocks in the nonvolatile memory is changed to a read only mode, and   after the data write operation to the blocks becomes prohibited and the data write operation mode is changed to the read only mode, the data write operation to the blocks will continue to be prohibited and the data write operation mode will continue to be maintained in the read only mode without determining whether or not the memory system is approaching the end of lifespan even after an external power supply is restarted and the memory system is turned on again.   
     
     
         2 . The memory system according to  claim 1 , wherein the controller is configured to store information that indicates the number of bad blocks in the nonvolatile memory. 
     
     
         3 . The memory system according to  claim 1 , wherein the controller is configured to store information that indicates the number of free blocks in the nonvolatile memory. 
     
     
         4 . The memory system according to  claim 1 , wherein the controller is configured to issue warning information after it is determined that the memory system is approaching the end of lifespan. 
     
     
         5 . The memory system according to  claim 1 , wherein in response to receiving a data write request from a host device connected to the memory system after the data write operation to the nonvolatile memory is prohibited, the controller is configured to return a notice indicating an error to the host devise without processing the data write request. 
     
     
         6 . The memory system according to  claim 1 , wherein
 the nonvolatile memory includes a NAND-type flash memory, and   the memory system includes an SSD.   
     
     
         7 . A memory system comprising:
 a nonvolatile memory including a plurality of blocks; and   a controller configured to:
 generate a free block by controlling the nonvolatile memory; 
 manage a number of free blocks in the nonvolatile memory; 
 manage a number of bad blocks in the nonvolatile memory; and 
 determine whether or not the memory system is approaching an end of lifespan on the basis of the number of free blocks or the number of bad blocks; wherein, 
   after the controller determines that the memory system is approaching the end of lifespan based on the number of free blocks or the number of bad blocks, the controller is configured to prohibit a data write operation to the blocks in the nonvolatile memory and to change a data write operation mode to a read only mode, and   after the data write operation to the blocks becomes prohibited and the data write operation mode is changed to the read only mode, the controller is configured to prohibit the data write operation and to process memory access in the read only mode without determining whether or not the memory system is approaching the end of lifespan even after an external power supply is restarted and the memory system is turned on again.   
     
     
         8 . The memory system according to  claim 7 , wherein the controller is configured to store information that indicates the number of bad blocks in the nonvolatile memory. 
     
     
         9 . The memory system according to  claim 7 , wherein the controller is configured to store information that indicates the number of free blocks in the nonvolatile memory. 
     
     
         10 . The memory system according to  claim 7 , wherein the controller is configured to issue warning information after the controller determines that the memory system is approaching the end of lifespan. 
     
     
         11 . The memory system according to  claim 7 , wherein in response to receiving a data write request from a host device connected to the memory system after the data write operation to the nonvolatile memory is prohibited, the controller is configured to return a notice indicating an error to the host devise without processing the data write request. 
     
     
         12 . The memory system according to  claim 7 , wherein
 the nonvolatile memory includes a NAND-type flash memory, and   the memory system includes an SSD.   
     
     
         13 . A method of controlling a memory system comprising a nonvolatile memory including a plurality of blocks, the method comprising:
 generating a free block by controlling the nonvolatile memory;   managing a number of free blocks in the nonvolatile memory;   managing a number of bad blocks in the nonvolatile memory; and   determining whether or not the memory system is approaching an end of lifespan on the basis of the number of free blocks or the number of bad blocks, wherein,   after determining that the memory system is approaching the end of lifespan based on the number of free blocks or the number of bad blocks, a data write operation to the blocks in the nonvolatile memory becomes prohibited and a data write operation mode to the blocks in the nonvolatile memory is changed to a read only mode, and   after the data write operation to the blocks becomes prohibited and the data write operation mode is changed to the read only mode, the data write operation to the blocks will continue to be prohibited and the data write operation mode will continue to be maintained in the read only mode without determining whether or not the memory system is approaching the end of lifespan even after an external power supply is restarted and the memory system is turned on again.   
     
     
         14 . The method according to  claim 13 , further comprising storing information that indicates the number of bad blocks in the nonvolatile memory. 
     
     
         15 . The method according to  claim 13 , further comprising storing information that indicates the number of free blocks in the nonvolatile memory. 
     
     
         16 . The method according to  claim 13 , further comprising issuing warning information after it is determined that the memory system is approaching the end of lifespan. 
     
     
         17 . The method according to  claim 13 , further comprising returning, in response to receiving a data write request from a host device connected to the memory system after the data write operation to the nonvolatile memory is prohibited, a notice indicating an error to the host devise without processing the data write request. 
     
     
         18 . The method according to  claim 13 , wherein
 the nonvolatile memory includes a NAND-type flash memory, and   the memory system includes an SSD.